I think the one thing most sci-fi authors have gotten wrong with their space futurism is the people - there won't be any. We are fast approaching the point where robots won't just be flying around in space taking pictures and recording data - they'll be building things, like big-ass solar power arrays, ore extraction and processing facilities, etc. I'm sure we'll see space-based vacation resorts for the extremely well-to-do, but it costs way to much to put human workers up there to do anything a robot can - and robots can do more and more (and more).

Humanity could soon be building huge structures in space one piece at a time, the way spiders spin their webs here on Earth.

A company called Tethers Unlimited is developing an in-space manufacturing system called "SpiderFab," which would use arachnidlike robots to put together large objects in orbit or beyond.

SpiderFab could help build big radio antennas, spacecraft booms and solar arrays in the next decade or so, said Rob Hoyt, CEO and chief scientist of Tethers Unlimited. But he has an even grander vision for the technology (and associated projects the company is working on) over the long haul. [Visions of the Future of Human Spaceflight]

"Our really long-term objective for all of this work is to eventually enable the use of in-situ resources to construct the infrastructure in space needed to support humanity's expansion throughout the solar system," Hoyt said March 4 during a presentation with NASA's Future In-Space Operations (FISO) working group.

Artist's illustration of a robot building a space structure as envisioned by Tethers Unlimited's "SpiderFab" concept.Artist's illustration of a robot building a space structure as envisioned by Tethers Unlimited's "SpiderFab" concept.

Bringing costs down

Hoyt believes that the current model of spacecraft manufacturing  in which everything is built and assembled on the ground, and is then launched in one piece  leaves plenty of room for improvement.

"It's a very expensive and time-consuming process, and also, the size of systems is somewhat limited by the size of the deployables that are possible to fold up and fit within a launch shroud," he said.

SpiderFab is an effort to decrease costs and increase efficiencies. The idea calls for launching raw materials, such as carbon fiber, to orbit. There, robots would transform these materials into truss substructures, and then assemble and integrate these pieces into larger systems.

The potential benefits of such an approach are substantial, Hoyt said.

"The primary one will be that we can deploy apertures and baselines that are much larger than we can currently fit into launch shrouds," he said. "The payoff of that will be higher power, higher resolution, higher sensitivity and higher bandwidth for a wide range of NASA, DoD [Department of Defense] and commercial space missions."

Furthermore, objects built in space can be sleeker and simpler than ones launched from the ground, since they don't need to survive the rigors of launch. That should lead to reductions in design complexity and system mass, which could lead to significant cost savings, Hoyt added.

Case studies

SpiderFab has received two rounds of funding from the NASA Innovative Advanced Concepts (NIAC) program, which aims to encourage the development of potentially game-changing space technologies.

According to Hoyt, case-study analyses conducted under the Phase 1 NIAC award indicated that SpiderFab could achieve order-of-magnitude performance improvements in systems in which "bigger is better"  components such as solar arrays and telescope parts. [Incredible Technology: Space Travel and Exploration]

As an example of SpiderFab's potential, Hoyt cited the proposed New Worlds Observer (NWO) space telescope, which would use a huge "starshade" to block out most of the light of a target star, thus allowing its orbiting exoplanets to be imaged directly.

The largest conventionally built starshade would be about 203 feet (62 meters) wide, Hoyt said. Employing on-orbit manufacturing with the same amount of mass would increase that diameter to 406 feet (124 m), allowing NWO to peer twice as close to target stars  and thus observe more planets, Hoyt added.

In addition, launching the starshade in raw-material form, rather than in finished form, reduces its volume by a factor of 30, thus allowing a smaller (and therefore cheaper) rocket to be used for the potential mission, Hoyt said.

"All those benefits combine to enable NASA to basically buy 16 times more habitable planets per taxpayer dollar," he said.

Tethers Unlimited has already built a machine that makes supporting truss structures here on Earth using a process akin to 3D printing. Here's an artist's concept of the "trusselator" technology at work in space.Tethers Unlimited has already built a machine that makes supporting truss structures here on Earth using a process akin to 3D printing. Here's an artist's concept of the "trusselator" technology at work in space.

How it would work

At the heart of the SpiderFab concept is a multiarmed robot that would fabricate structural elements with one "spinneret" and use another one to join these pieces together as it crawls about on the ever-growing "web."

Tethers Unlimited, which is based in Bothell, Washington, is working to develop the various technologies required to pull off such an ambitious vision, Hoyt said.

For example, in a project funded by NASA's Small Business Innovation Research (SBIR) program, the company already built a machine that creates lightweight structural trusses from raw carbon-fiber spools, using a process akin to 3D printing.

This "trusselator," which is about the size of a microwave oven, can churn out truss  the type of stuff that could be put together to form a spacecraft boom and other systems  at the rate of 2 inches (5 centimeters) per minute, Hoyt said.

"Under the NIAC and SBIR work, I think we've already validated the basic feasibility of the key processes required" for the broad SpiderFab concept, he said.

The team is currently working on a second-generation trusselator, and hopes to have a prototype ready by early summer. Tethers Unlimited wants to launch a small "MakerSat" a couple of years from now to demonstrate the process on orbit. This spacecraft may end up being a CubeSat deployed from the International Space Station, Hoyt said.

The company has also bought a commercially available Baxter robot, and is using the machine to learn how to assemble trusses robotically. Hoyt and his colleagues will continue to develop and refine this process on the ground, and then aim to launch a "MakerSat 2" to prove it out in space  perhaps by building the truss structure for a big starshade.

"In a perfect world  if funding flowed and the contracting process didn't drag on forever  we think we could get to be able to build very large support structures for antennas and solar arrays, and those sorts of components, in the early 2020s," Hoyt said.

The RulesCopper- behave toward others to elicit treatment you would like (the manipulative rule)Gold- treat others how you would like them to treat you (the self regard rule)Platinum- treat others the way they would like to be treated (the PC rule)

Sit back and take a ride from the Sun to Jupiter, at the speed of light.
Animator Alphonse Swinehart made this video to illustrate the sheer mind-boggling scale of the solar system.
It isn't completely accurate, as Swinehart admits. "I've taken liberties with certain things like the alignment of planets and asteroids," he says, "but overall I've kept the size and distances of all the objects as accurate as possible."

He has also purposely ignored some counter-intuitive physical effects that come into play as you approach light speed. For instance, subjective time slows down, and your vision would also be weirdly distorted.

What the video does capture, with a simple clarity, is the sheer size of space. Even at the fastest possible speed, simply getting to Jupiter takes the better part of an hour.
You may want to get a drink and something to eat, because this is going to take a while.
______________________________________________

Whack up to full screen and enjoy. Then contemplate just how frickin tiny and alone we really are.

Originally Posted by Steely Glint

It's actually the original French billion, which is bi-million, which is a million to the power of 2. We adopted the word, and then they changed it, presumably as revenge for Crecy and Agincourt, and then the treasonous Americans adopted the new French usage and spread it all over the world. And now we have to use it.

New Horizons snaps remarkable hi-res images of Pluto as it treks onward ...

Originally Posted by Steely Glint

It's actually the original French billion, which is bi-million, which is a million to the power of 2. We adopted the word, and then they changed it, presumably as revenge for Crecy and Agincourt, and then the treasonous Americans adopted the new French usage and spread it all over the world. And now we have to use it.

Originally Posted by http://www.slate.com/blogs/bad_astronomy/2015/10/14/weird_star_strange_dips_in_brightness_are_a_bit_ba ffling.html

Did Astronomers Find Evidence of an Alien Civilization? (Probably Not. But Still Cool.)By Phil Plait

What is causing the star KIC 8462852 to behave so strangely? A huge belt of debris around it, or ... something else?A paper by a team of astronomers is getting some notice because of aliens.Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!

Now let’s have a care here. The paper doesn’t mention aliens, and it doesn’t even imply aliens. Not directly, at least. But the astronomers found a star so odd, with behavior so difficult to explain, that it’s clear something weird is happening there. And some of the astronomers who did the work are now looking into the idea that what they’ve found might (might!) be due to aliens.

But don’t let this idea run away with you (as it has with some folks on social media and, no doubt, will in some sketchier “media” outlets any minute now). The scientists involved are being very skeptical and approaching this the right way: more of an interested “Hey, why not?” follow-up, as opposed to the Hollywood renegade astronomer who just knows it’s aliens but (fist shaking in the air) just can’t convince those uptight Big Astro sellouts!

But it’s cool either way.

OK, so first, what’s the science?

The star is called KIC 8462852, and it’s one of more than a hundred thousand stars that was observed by NASA’s Kepler mission. Kepler stared at these stars, looking for dips in their brightness. These very slight dimmings can be due to many factors, but one is if the star has planets, and one (or more) of them orbits the star in such a way that it passes directly in front of the star as seen from Earth. If it does—what we call a transit—we see a tiny diminution of starlight, usually by less than a percent.

Thousands of exoplanets have been found this way. Usually the planet is on a short orbit, so the dip we see is periodic, repeating every few days, weeks, or months, depending on the size of the planet’s orbit.

KIC 8462852 is a star somewhat more massive, hotter, and brighter than the Sun. It’s about 1,500 light-years away, a decent distance, so it’s too faint to see with the naked eye. The Kepler data for the star are pretty bizarre: There are dips in the light, but they aren’t periodic. They can be very deep; one dropped the amount of starlight by 15 percent, and another by a whopping 22 percent!

Straight away, we know we’re not dealing with a planet here. Even a Jupiter-sized planet only blocks roughly 1 percent of this kind of star’s light, and that’s about as big as a planet gets. It can’t be due to a star, either; we’d see it if it were. And the lack of a regular, repeating signal belies both of these as well. Whatever is blocking the star is big, though, up to half the width of the star itself!

Also, it turns out there are lots of these dips in the star’s light. Hundreds. And they don’t seem to be periodic at all. They have odd shapes to them, too. A planet blocking a star’s light will have a generally symmetric dip; the light fades a little, remains steady at that level, then goes back up later. The dip at 800 days in the KIC 8462852 data doesn’t do that; it drops slowly, then rises more rapidly. Another one at 1,500 days has a series of blips up and down inside the main dips. There’s also an apparent change in brightness that seems to go up and down roughly every 20 days for weeks, then disappears completely. It’s likely just random transits, but still. It’s bizarre.

The authors of the paper went to some trouble to eliminate obvious causes. It’s not something in the telescope or the processing; the dips are real. It’s not due to starspots (like sunspots, but on another star). My first thought was some sort of planetary collision, like the impact that created the Moon out of the Earth billions of years ago; that would create a lot of debris and dust clouds. These chunks and clouds orbiting the star would then cause a series of transits that could reproduce what’s seen.

The problem with that is that there’s no excess of infrared light from the star. Dust created in such impacts warms up and glows in the IR. We know how much IR stars like KIC 8462852 give off, and we see just the right amount from it, no more. The lack of that glow means no (or very little) dust.

The last idea the astronomers looked at was a series of comets orbiting the star. These could be surrounded by clouds of gas and other material that could produce the dips seen. The lack of IR is puzzling in that case, but not too damning. If another star happened to pass nearby, then its gravity could disturb the first star’s Oort cloud, the region billions of kilometers out where we think most (if not all) stars have billions of icy objects. This disturbance could send these ice chunks flying down toward the star, where they could break up, creating all those weird dips—ices in them would heat up, blow off as a gas, and could explain the odd shapes of the dips detected, too.

And, as it happens, there is another star pretty close to KIC 8462852; a small red dwarf about 130 billion kilometers out. That’s close enough to affect the Oort cloud.

This doesn’t close the case, though. Comets are a good guess, but it’s hard to imagine a scenario where they could completely block 22 percent of the light from a star; that’s a huge amount. Really huge.

So where does that leave us?

Wondering if there might be more to this, Tabetha Boyajian, the lead author on the paper, showed the results to Jason Wright, an astronomer who studies exoplanets and, not coincidentally, has researched how to look for signatures of advanced alien civilizations in Kepler data.

Yes, seriously.

Get this:

Look at our own civilization. We consume ever-increasing amounts of power, and are always looking for bigger sources. Fossil, nuclear, solar, wind … Decades ago, physicist Freeman Dyson popularized an interesting idea: What if we built thousands of gigantic solar panels, kilometers across, and put them in orbit around the Sun? They’d capture sunlight, convert it to energy, and that could be beamed to Earth for our use. Need more power? Build more panels! An advanced civilization could eventually build millions, billions of them.

This idea evolved into what’s called a Dyson Sphere, a gigantic sphere that completely encloses a star. It was popular back in the 1970s and 80s; there was even an episode of Star Trek: The Next Generation about one. Dyson never really meant that we’d build an actual sphere; just lots of little panels that might mimic one.

But it raises an interesting possibility for detecting alien life. Such a sphere would be dark in visible light but emit a lot of infrared. People have looked for them, but we’ve never seen one (obviously).

Which brings us back to KIC 8462852. What if we caught an advanced alien civilization in the process of building such an artifact? Huge panels (or clusters of them) hundreds of thousands of kilometers across, and oddly-shaped, could produce the dips we see in that star’s light.

Now I imagine some of you might expect me to rail against this idea, call it ridiculous, and pooh-pooh the notion of aliens and all that

Well, surprise! I actually kinda like it. I’m not saying it’s right, mind you, just that it’s interesting. Wright isn’t some wild-eyed crackpot; he’s a professional astronomer with a solid background. As he told me when I talked to him over the phone, there’s “a need to hypothesize, but we should also approach it skeptically” (paraphrasing a tweet by another astronomer, David Grinspoon), with which I wholeheartedly agree.

Look, I think it’s pretty obvious this scenario is, um, unlikely. But hey, why not? It’s easy enough to get follow-up observations of the star to check the idea out. It’s low probability but high stakes, so probably worth a shot. And it’s not exactly science fiction; Wright and a few other astronomers have submitted a paper (pending publication) to the prestigious Astrophysical Journal examining the physics of these structures and detailing how they could be detected around other stars.

As reported in the Atlantic (which is what started all the social media interest in the first place), Wright and Boyajian are indeed proposing to use a radio telescope to look for signals from the star. An alien civilization building such a structure might leak (or broadcast!) radio waves that could be detectable from 1,500 light-years away. That’s the whole basis of SETI, the Search for Extraterrestrial Intelligence (see the movie Contact, or better yet read the book, for more on this). Telescope time is controlled by a committee, and it’s not clear if the proposal will pass or not. I hope so; it shouldn’t take too much telescope time, and under modest assumptions it shouldn’t be too hard to detect a signal.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

Sure it'll come down to a natural explanation. But the speculation is fantastic.

Originally Posted by Steely Glint

It's actually the original French billion, which is bi-million, which is a million to the power of 2. We adopted the word, and then they changed it, presumably as revenge for Crecy and Agincourt, and then the treasonous Americans adopted the new French usage and spread it all over the world. And now we have to use it.

1500ly is a little too close for comfort if you ask me. Whatever it is we're seeing these scrubs get up to around their star, they were doing it about the time Rome fell. So lord knows what they'd be capable of right now, as I write this.

I for one am hoping for space dust as the explanation.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

It is pretty close. If it were an alien civilization, then it would mean that they have no interest in systems outside their own, or they know that our system has a life bearing planet. That we're pretty uncolonized would imply certain things.

But it's probably just space dust or something. A shattered planet could be pretty cool too.

Assuming KIC[numbers] *is* their home system, not some outpost on their frontier.

I don't think we need to worry about being colonized per say, because why bother, but what if they show up in our system, and start building a dyson swarm round the sun? We'd be like "uh, excuse me, do you mind? We're fucking using that" but they don't hear because they only perceive the upper 6 dimensions or some shit.

Alternatively, if they are only in their own system that kind of implies things like the alcubierre drive are a wash which is pretty meh.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

It is pretty close. If it were an alien civilization, then it would mean that they have no interest in systems outside their own, or they know that our system has a life bearing planet. That we're pretty uncolonized would imply certain things.

But it's probably just space dust or something. A shattered planet could be pretty cool too.

It could be the former, although science is going fast there is still no realistically plausible (let alone implemented) method of getting Faster Than Light travel. Even in thousands more years there might never be. In which case its entirely possible that the universe has lots of planets with sentient life on it but has not been colonised because the entire concept of colonisation in practice is implausible and just not worth it.

Originally Posted by Ominous Gamer

Being upset is understandable, but be upset at yourself for poor planning, not at the world by acting like a spoiled bitch during an interview.

It could be the former, although science is going fast there is still no realistically plausible (let alone implemented) method of getting Faster Than Light travel. Even in thousands more years there might never be. In which case its entirely possible that the universe has lots of planets with sentient life on it but has not been colonised because the entire concept of colonisation in practice is implausible and just not worth it.

Hey, I was going to post that! Or they're already here, secretly, as shapeshifting reptillians.

But without FTL travel I don't think colonisation is practical unless you're approaching the death of your sun. Hell, I expect humans to terraform the rest of the solar system first, and even that is quite a feat.

Alternatively, if they are only in their own system that kind of implies things like the alcubierre drive are a wash which is pretty meh.

Outpost or not, if they're starting to construct a Dyson sphere before they've run out of places to colonize it would mean that FTL travel is at least impractical. It has to at least be harder to shift population to other places with easy energy & resources than to build megastructures to support them.

I wouldn't expect a communication or annihilation attempt. Earth is pretty obviously life bearing, but I don't think aliens that far away would have any way to know there was sapient life here. But all indications are that life bearing planets should still interesting in this galaxy, and their lack of presence suggests that a visit is impractical even for them.

1500 LY is probably too far away for us to tell if they're broadcasting anything or not. Any transmission that isn't point-to-point would be extremely weak by the time it got to us. I doubt we'd be able to notice any signal they weren't intentionally beaming out to us.

The other implication if that were an actual alien race would be that it'd suggest the Great Filter is still ahead of us.

Outpost or not, if they're starting to construct a Dyson sphere before they've run out of places to colonize it would mean that FTL travel is at least impractical. It has to at least be harder to shift population to other places with easy energy & resources than to build megastructures to support them.

To be clear, a dyson sphere (shell/swarm) as originally conceived isn't for living on, it's for harvesting energy.

And not necessarily; constructing one of those beasts could simply how they generate enough energy to travel between stars. Alternatively, they could just find constructing fuckhueg space structures more efficient than terraforming worlds, or perhaps they have cultural reasons why they don't like terraforming and prefer to leave the planets they find in their natural state (this is actually the official position of NASA). Or maybe it's a vanity project? Or maybe it's simply some artefact of their technology which is beyond our comprehension (just think how you'd explain what you do for a living to someone from 500 years ago).

But without FTL travel I don't think colonisation is practical unless you're approaching the death of your sun. Hell, I expect humans to terraform the rest of the solar system first, and even that is quite a feat.

IDK, if we found an Earthlike around Alpha Centauri, I think we could put a colony there inside a couple of centuries if we put our minds to it and perhaps four if we don't; with currently existing technologies we could get there inside a century and with conceivable future technologies I think we could get there in just south of a decade.

Meanwhile, IMHO terraforming is overrated. You can change a worlds atmosphere, you can add oceans, you can (somehow, I guess) find a way to give the world a magnetic field to keep people on the surface from being overly irradiated but you can't add mass to the planet and give it anywhere close to the 1g we evolved to live in. We know that microgravity causes all kinds of health-complications in astronauts from loss of muscle and bone mass to vision damage and god knows what else; all easily manageable with trips measured in months but people living our their lives in low gravity? Being born in low gravity? Obviously, the 0.4g on (say) Mars isn't going to be as bad as what the astronauts experience on the ISS but I think there's a good chance we're going to see health-complications for any permanent Martian population. "Come Live on Mars, die sooner" < not a winning slogan.

Oh, and the other terrestrial worlds have way less gravity than even Mars. Only Venus is really suitable for terraforming. And Venus needs a lot of work doing to it.

Is that really any more impractical than just... popping to Alpha Centauri, Barnard's Star, Sirius if we happen to find an Earthlike around one of them?

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

To be clear, a dyson sphere (shell/swarm) as originally conceived isn't for living on, it's for harvesting energy.

Yes, I know. I was assuming it was a swarm of solar panels supporting people on a planet or maybe culture orbitals or something, not an actual sphere being built in bits.

And not necessarily; constructing one of those beasts could simply how they generate enough energy to travel between stars. Alternatively, they could just find constructing fuckhueg space structures more efficient than terraforming worlds, or perhaps they have cultural reasons why they don't like terraforming and prefer to leave the planets they find in their natural state (this is actually the official position of NASA). Or maybe it's a vanity project? Or maybe it's simply some artefact of their technology which is beyond our comprehension (just think how you'd explain what you do for a living to someone from 500 years ago).

I was careful to always say "impractical" and not "impossible". If they need to build a dyson sphere to get the energy to send out spaceships, moving population via spaceship is probably impractical. If it weren't, they'd probably just spread out instead of getting all their energy from a single star. They're not going to have large-scale FTL.

I think NASA was giving about half a metric ton of mass-energy for a warp drive? A dyson sphere might be a reasonable investment for starship construction if starships are prohibitively expensive, and for some reason your civilization really needs/wants them anyways.

On vanity projects, it seems unlikely. The main reason is that for it to be a vanity project that would imply a pretty massive civilizational level of power, and it's hard to believe that they'd be confined to one system with that level of power if travel to other systems weren't extremely throttled somehow. There's a good chance they'd at least send out slowboats by the time they started building stellar scale monuments to themselves. There's a limit to how widespread they can be if this is the first time we've detected them. Not impossible that it's a vanity project, just unlikely IMO.

Basically what I keep getting at is that if that actually is bits of a megastructure or some other result of intelligent life we're seeing, then influencing the universe on that scale without colonizing the galaxy first implies some sort of throttle on colonization. An attitude-based throttle (some sort of prime directive type thing, like what you suggested) would work. We should probably expect to be in the same boat as them either way though - that they're that far developed and haven't colonized the galaxy means that there's very likely good reason for that.

Yes, I know. I was assuming it was a swarm of solar panels supporting people on a planet or maybe culture orbitals or something, not an actual sphere being built in bits.

Sorry dude.

I was careful to always say "impractical" and not "impossible". If they need to build a dyson sphere to get the energy to send out spaceships, moving population via spaceship is probably impractical. If it weren't, they'd probably just spread out instead of getting all their energy from a single star. They're not going to have large-scale FTL.

Well, this may be a bit like the ancients looking at nuclear weapons and all the cost and energy that goes into producing them (imagine the cost of a single device would by easily equal to the GDP of several medieval European kingdoms, if not way more), and wondering "wouldn't it be cheaper to just send an army to massacre the population?" I mean, yeah, technically, it would... but you're not fully appreciating the context in which these things are actually being built.

On vanity projects, it seems unlikely. The main reason is that for it to be a vanity project that would imply a pretty massive civilizational level of power, and it's hard to believe that they'd be confined to one system with that level of power if travel to other systems weren't extremely throttled somehow. There's a good chance they'd at least send out slowboats by the time they started building stellar scale monuments to themselves. There's a limit to how widespread they can be if this is the first time we've detected them. Not impossible that it's a vanity project, just unlikely IMO.

We don't actually know that they're confined to one system. We've just seen them in one system, it doesn't mean they aren't in others where we haven't seen them. We only saw them here, assuming we saw anything at all, because they were undertaking a vast construction project, they could be in literally 100s or 1000s of star systems where they haven't done this yet (as of 500 BC) and we wouldn't see shit.

In fact, no - even if they have done this a few times we still might not see it. It took some guys taking a close look at data from this one star and then writing a paper about it for us to notice something weird was going on there. We've catalogued millions of stars which might mean 10s or 100s of thousands of stars in the area of space where this hypothetical race might theoretically hold sway. Have we looked at all of them for weird dips in starlight? I'm betting no.

Basically what I keep getting at is that if that actually is bits of a megastructure or some other result of intelligent life we're seeing, then influencing the universe on that scale without colonizing the galaxy first implies some sort of throttle on colonization. An attitude-based throttle (some sort of prime directive type thing, like what you suggested) would work. We should probably expect to be in the same boat as them either way though - that they're that far developed and haven't colonized the galaxy means that there's very likely good reason for that.

Maybe they're doing it right now. The period of time between "single planet civilisation" and "has colonized the galaxy" is probably millions of years, especially if they're doing so via STL.

That said, you may well be right; the seeming lack of intelligent life kicking around the galaxy is puzzling and none of the explanations I have heard sound compelling to me. It seems we're missing an important piece of the puzzle. Perhaps advanced civilisations come to understand the physical universe in ways that simply make spreading out like that irrelevant.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

IDK, if we found an Earthlike around Alpha Centauri, I think we could put a colony there inside a couple of centuries if we put our minds to it and perhaps four if we don't; with currently existing technologies we could get there inside a century and with conceivable future technologies I think we could get there in just south of a decade.

Meanwhile, IMHO terraforming is overrated. You can change a worlds atmosphere, you can add oceans, you can (somehow, I guess) find a way to give the world a magnetic field to keep people on the surface from being overly irradiated but you can't add mass to the planet and give it anywhere close to the 1g we evolved to live in. We know that microgravity causes all kinds of health-complications in astronauts from loss of muscle and bone mass to vision damage and god knows what else; all easily manageable with trips measured in months but people living our their lives in low gravity? Being born in low gravity? Obviously, the 0.4g on (say) Mars isn't going to be as bad as what the astronauts experience on the ISS but I think there's a good chance we're going to see health-complications for any permanent Martian population. "Come Live on Mars, die sooner" < not a winning slogan.

Oh, and the other terrestrial worlds have way less gravity than even Mars. Only Venus is really suitable for terraforming. And Venus needs a lot of work doing to it.

Is that really any more impractical than just... popping to Alpha Centauri, Barnard's Star, Sirius if we happen to find an Earthlike around one of them?

I get where you're coming from, but first of all you're relying on the big if that a possibly earthlike planet exists relatively near us. But wouldn't it also be be very likely that such a planet would still not be exactly like earth, and require similar terraforming as, say, Mars would, and have the exact same problems you've described here in addition to the problems of getting there in the first place, and the additional problem of getting the resources there to do this? So yeah, I do think terraforming in our own system is likely to happen first because you would need it as a step to go to another galaxy.

And I thought the majority of the issues you've described are due to weightlessness, and would be significantly reduced (or even absent) at low gravity as opposed to (almost) none, and IIRC most proposals for centrifuge like stations aimed for a lower artificial gravity than earth's. Then again, I don't think we know much about this at all right now so it's mostly speculation, and there's likely problems we don't know about yet. Which, I suppose, would be easier to test on a nearby planet instead of flying to another solar system and hope it will be okay (not to mention the health problems of a decade long space flight). Optimistically people would simply adapt to their home planet, and as long as you don't travel you'll be fine. Babies born there might even be better adapted (though have bigger problems returning to earth), with an emphasis on 'might' because it might also be impossible to give birth to a healthy baby under the circumstances. And again, is it that likely that the coincidental nearby earthlike planes are exactly like earth and won't have these problem toos?

Also your gravity claim is untrue, the other terrestrial planets do not have "way less" gravity than Mars. There's only Mercury, which has almost identical surface gravity (0,38g instead of 0,376g, so actually marginally bigger), and Venus, which is closer to Earth at 0,905g. Unless you meant minor planets and moons, which are indeed a lot lower.

Anyway, talking about why they haven't reached us yet, your post describes it might be possible to colonize a near star, 1,500ly away is quite a lot more and might simply be impractical without FTL technology.

Well, this may be a bit like the ancients looking at nuclear weapons and all the cost and energy that goes into producing them (imagine the cost of a single device would by easily equal to the GDP of several medieval European kingdoms, if not way more), and wondering "wouldn't it be cheaper to just send an army to massacre the population?" I mean, yeah, technically, it would... but you're not fully appreciating the context in which these things are actually being built.

We have nuclear weapons because they're cheaper/easier than the alternatives, including sending a sword wielding army in to slaughter everyone. I'm not sure your example's significantly different from what I'm saying.

We don't actually know that they're confined to one system. We've just seen them in one system, it doesn't mean they aren't in others where we haven't seen them. We only saw them here, assuming we saw anything at all, because they were undertaking a vast construction project, they could be in literally 100s or 1000s of star systems where they haven't done this yet (as of 500 BC) and we wouldn't see shit.

We don't know, but we do know they're not in this system so there must be some reason for that. We also know they've not left similar evidence in any of the other systems we've been looking at. By starting construction on a Dyson sphere or Matrioshka brain or whatever 1500 years ago, we can tell that it is not due to a lack of capability, which means there is another reason.

This is basically your medieval guy looking at the bombs and saying "Bombs are pretty complicated, but swords are pretty easy, but they use bombs instead of swords, therefore bombs must be superior in some way." Further, this medieval guy could also conclude that just building bigger and longer swords isn't going to get him very far in the art of war.

Maybe they're doing it right now. The period of time between "single planet civilisation" and "has colonized the galaxy" is probably millions of years, especially if they're doing so via STL.

Even at STL, that we caught them in the perfect window, where we're close enough to their expansion zone to see them building dyson spheres in their core worlds, but far enough from their expansion zone that they haven't gotten here yet - out of all the billions of years they and we could have existed, that's pretty unlikely. Even if it takes them millions of years to colonize the galaxy, that's still the blink of an eye cosmically, and we're still deep in the unresolved Fermi paradox. If colonization happens at all, then us being the second race in the galaxy to be ever be capable of it, and also existing this late in the game but exactly in the window between when the first race starts and finishes, that's all a pretty massive coincidence*. I mean, the probability is non-zero, but it's not very large.

The most likely solution to this if that actually is some kind of megastructure is that sapient alien life is actually fairly common, so the fact that we exist in the window necessary to see these other guys isn't that incredibly improbable. Further, colonization must be an inferior option to building whatever it is they're building for some reason, otherwise somebody would already be here and we wouldn't have spent so long gazing into an apparently empty cosmos.

If you grant these two things, we can then take it further and say that the colonization throttle is unlikely to be ethical or some sort of 'prime directive'. If it were, it would only take one race (of the many that have existed) to cheat and behave unethically for the universe to no longer match our observations. So the throttle is most likely logistical or engineering based. It's probably safe to say it's not engineering based - we could build a generation ship within the next fifty years if we really really wanted to. Which leaves logistical - they don't do it because doing this other thing is just a better use of their resources (broadly defined). The same reason we drop bombs instead of sending in men with swords - we certainly could do the latter, but the former is so much cheaper, safer, and more effective that it would be stupid to do so.
*edit: Other possibility, maybe they are the first race, but we're not the second. This would be much more likely than them being first and us second. This possibility ought to be terrifying.

I get where you're coming from, but first of all you're relying on the big if that a possibly earthlike planet exists relatively near us. But wouldn't it also be be very likely that such a planet would still not be exactly like earth, and require similar terraforming as, say, Mars would, and have the exact same problems you've described here in addition to the problems of getting there in the first place, and the additional problem of getting the resources there to do this? So yeah, I do think terraforming in our own system is likely to happen first because you would need it as a step to go to another galaxy.

I forgot to write that I think artificial habitats are a more realistic prospect for human space habitation than living on planetary surfaces, in this or any other system.

P.S. if you put engines on a space habitat now it's called a generation ship.

And I thought the majority of the issues you've described are due to weightlessness, and would be significantly reduced (or even absent) at low gravity as opposed to (almost) none, and IIRC most proposals for centrifuge like stations aimed for a lower artificial gravity than earth's. Then again, I don't think we know much about this at all right now so it's mostly speculation, and there's likely problems we don't know about yet. Which, I suppose, would be easier to test on a nearby planet instead of flying to another solar system and hope it will be okay (not to mention the health problems of a decade long space flight). Optimistically people would simply adapt to their home planet, and as long as you don't travel you'll be fine. Babies born there might even be better adapted (though have bigger problems returning to earth), with an emphasis on 'might' because it might also be impossible to give birth to a healthy baby under the circumstances. And again, is it that likely that the coincidental nearby earthlike planes are exactly like earth and won't have these problem toos?

I think the idea of a permanent presence on Mars al la Antarctica (these places have quite a lot in common actually) is a good idea, I just don't think a proper colony with people being born, living out their lives and dying there is viable - unless I'm wrong about the gravity thing, which I'm very happy to be.

Also your gravity claim is untrue, the other terrestrial planets do not have "way less" gravity than Mars. There's only Mercury, which has almost identical surface gravity (0,38g instead of 0,376g, so actually marginally bigger), and Venus, which is closer to Earth at 0,905g. Unless you meant minor planets and moons, which are indeed a lot lower.

I did.

Anyway, talking about why they haven't reached us yet, your post describes it might be possible to colonize a near star, 1,500ly away is quite a lot more and might simply be impractical without FTL technology.

I'm not so sure. If you can go 0.8 or 0.9c with some futuristic proposition drive then I think the time dilation gets to the point where the travellers should live to see their destination. The logistical challenge for going to nearby stars is the same as the one for going to distant stars; you just need to be able to build a ship that'll keep people alive for years or decades.

But you wouldn't be expanding your own civilisation that way, just starting new ones.

Your other option is you colonize nearby habitable exoplanets, wait a couple of centuries until they're supporting developed cultures of their own then *they* send out colony ships to worlds near to them and so on and so on. After a few million years of this, your dudes are probably on a significant %age of the milky way.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

We have nuclear weapons because they're cheaper/easier than the alternatives, including sending a sword wielding army in to slaughter everyone. I'm not sure your example's significantly different from what I'm saying.

But that's not why we have them. To understand why we have them, especially when almost everyone agrees they are, basically, awful you'd have to first understand the nature of modern warfare, the interdependent nature of modern societies and the understand the geopolitical context of the cold war that lead to us building so many of them; none of which would be readily apparent to a medieval dude just trying to understand the things in isolation.

Likewise, it is not possible to make a proper cost-benefit analysis of the spess aliens building dyson spheres in the constellation of cygnus but not rocking up to Sol in the F/SLT ships because we don't know the political, technological and cultural context in which those decisions were made.

We don't know, but we do know they're not in this system so there must be some reason for that. We also know they've not left similar evidence in any of the other systems we've been looking at. By starting construction on a Dyson sphere or Matrioshka brain or whatever 1500 years ago, we can tell that it is not due to a lack of capability, which means there is another reason.

Again; millions upon millions of known stars. Billions more unknown; they could be doing this all over the place and there's no reason to assume we would have noticed. They're not in this system, and there must be some reason for that? The reason is that within 2000 ly of earth there are approximately 80 million stars. Enough to keep anyone busy for a mere few thousand or even single digit million. Even dyson sphere builders.

This is basically your medieval guy looking at the bombs and saying "Bombs are pretty complicated, but swords are pretty easy, but they use bombs instead of swords, therefore bombs must be superior in some way." Further, this medieval guy could also conclude that just building bigger and longer swords isn't going to get him very far in the art of war.

Even at STL, that we caught them in the perfect window, where we're close enough to their expansion zone to see them building dyson spheres in their core worlds, but far enough from their expansion zone that they haven't gotten here yet - out of all the billions of years they and we could have existed, that's pretty unlikely.

Of all the infinite number of possible situations that could exist, and given one of them is pretty unlikely.

Consider; all the millions of years humanity existed before we discovered this star and all the millions of years of years it will (hopefully) continue to exist after we figure out that, no false alarm, it's actually just space dust; how astronomically unlikely is that you and I both happened to have been born within that tiny window, and given all the millions of humans who rich enough to afford the internet we both *just happened* to both be interested enough in computer games made by one particular company to end up on the Atari forums, interested enough in current affairs to move to community chat and then invested enough in the community to make the move over to here? If you think about it, this very conversation is almost astronomically improbably, and yet here it is.

Even if it takes them millions of years to colonize the galaxy, that's still the blink of an eye cosmically, and we're still deep in the unresolved Fermi paradox. If colonization happens at all, then us being the second race in the galaxy to be ever be capable of it, and also existing this late in the game but exactly in the window between when the first race starts and finishes, that's all a pretty massive coincidence*. I mean, the probability is non-zero, but it's not very large.

I have no answer to this. But then, there is no good answer to the Fermi paradox, I haven't heard one that doesn't contain an unacceptable level of bullshit & assumptions.

Obviously, we're missing something. I have no idea what. Better minds than mine have no idea either, soooo

The most likely solution to this if that actually is some kind of megastructure is that sapient alien life is actually fairly common, so the fact that we exist in the window necessary to see these other guys isn't that incredibly improbable. Further, colonization must be an inferior option to building whatever it is they're building for some reason, otherwise somebody would already be here and we wouldn't have spent so long gazing into an apparently empty cosmos.

Trouble is, you build one of these things and then you sit around for a few million years and then what? Stop expanding, stop growing? Eventually you're going to want another one. The problem doesn't go away.

If you grant these two things, we can then take it further and say that the colonization throttle is unlikely to be ethical or some sort of 'prime directive'. If it were, it would only take one race (of the many that have existed) to cheat and behave unethically for the universe to no longer match our observations. So the throttle is most likely logistical or engineering based. It's probably safe to say it's not engineering based - we could build a generation ship within the next fifty years if we really really wanted to. Which leaves logistical - they don't do it because doing this other thing is just a better use of their resources (broadly defined). The same reason we drop bombs instead of sending in men with swords - we certainly could do the latter, but the former is so much cheaper, safer, and more effective that it would be stupid to do so.

Like all solutions to the Fermi paradox this seems to rely on a uniformity of motive that I just find profoundly unconvincing.

*edit: Other possibility, maybe they are the first race, but we're not the second. This would be much more likely than them being first and us second. This possibility ought to be terrifying.

If it's a clear night and you're in the Northern hemisphere, if you find Vega then imagine a line between Vega and Deneb, then about 75% of the way along the line you'll find the patch of sky we're talking about. You can't see the star because it's too faint but you're looking in the right direction.

Next clear night I want everyone reading this to go out, find that patch of sky stare and it for a few moments and then say, out loud, "Don't try any shit"

Just to be on the safe side.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

But that's not why we have them. To understand why we have them, especially when almost everyone agrees they are, basically, awful you'd have to first understand the nature of modern warfare, the interdependent nature of modern societies and the understand the geopolitical context of the cold war that lead to us building so many of them; none of which would be readily apparent to a medieval dude just trying to understand the things in isolation.

In other words, they are superior in some way. It's easier than trying to maintain an army of swordsmen large enough to guarantee annihilation of our enemies within quick striking distance of them. You don't need to understand why they're superior to understand that they are.

Likewise, it is not possible to make a proper cost-benefit analysis of the spess aliens building dyson spheres in the constellation of cygnus but not rocking up to Sol in the F/SLT ships because we don't know the political, technological and cultural context in which those decisions were made.

It's unlikely that they're the first. If there are two sapient races, then there are almost certainly many. If the reasons are political or cultural, then you need to assume that all races have political or cultural reasons not to do it. I consider this unlikely, but if it were true there's no reason to assume we'll be any different at that stage. The difference between this and assuming that there is some logistical reason not to do it is negligible right now.

Again; millions upon millions of known stars. Billions more unknown; they could be doing this all over the place and there's no reason to assume we would have noticed. They're not in this system, and there must be some reason for that? The reason is that within 2000 ly of earth there are approximately 80 million stars. Enough to keep anyone busy for a mere few thousand or even single digit million. Even dyson sphere builders.

This is that massive coincidence again, though. On further reflection of the likelihood of this, I can only pray that this isn't the case. For colonization to be worth doing, and for it to not have happened until now, and for sapient life to be so common that two races could coexist so close in time and space, it won't matter how far off their expansion horizon is from us - we are almost certainly thoroughly fucked. The Great Filter will be ahead of us, and it is going to be angry.

Of all the infinite number of possible situations that could exist, and given one of them is pretty unlikely.

Consider; all the millions of years humanity existed before we discovered this star and all the millions of years of years it will (hopefully) continue to exist after we figure out that, no false alarm, it's actually just space dust; how astronomically unlikely is that you and I both happened to have been born within that tiny window, and given all the millions of humans who rich enough to afford the internet we both *just happened* to both be interested enough in computer games made by one particular company to end up on the Atari forums, interested enough in current affairs to move to community chat and then invested enough in the community to make the move over to here? If you think about it, this very conversation is almost astronomically improbably, and yet here it is.

This is solved by a version of the anthropic principle. Our conversation here is nothing special. I could be having a similar conversation on some other forum, or with someone else. If you weren't here, I'd probably be doing something equivalent with EyeKhan. Right now, other people besides the two of us are probably having similar conversations. Nothing is special about what we're doing right now, so it's a believable outcome.

The same cannot be said about the idea that they exist, are colonizing the galaxy, but haven't gotten to us yet. That would place both us and them in a privileged position in the history of the galaxy. It's not impossible, but it's extremely unlikely, only more so because the galaxy has been capable of supporting life such as our for billions of years before now.

The situation can only be resolved by assuming there's nothing special about our situation. We aren't privileged. If we had existed at some other time in the the past or next billion years instead, or in some other galaxy, we would still be able to look out and see most stars empty, with a scant handful stars having megastructures built around them. The only way this can be true (if that is a megastructure we're seeing), the only way to maintain our unprivileged status, is if interstellar colonization just isn't a route civilizations go down, for whatever reason. Otherwise, the universe doesn't meet what we should expect as unprivileged observers.

Trouble is, you build one of these things and then you sit around for a few million years and then what? Stop expanding, stop growing? Eventually you're going to want another one. The problem doesn't go away.

Maybe you don't need more? Or maybe one will keep you for an extremely long period of time? If you slow expansion down so galactic colonization takes billions rather than millions of years, that might also work. In this case, we should be able to spot other stars with similar structures being built around them, because it's very unlikely that they're the only ones that far along.

Like all solutions to the Fermi paradox this seems to rely on a uniformity of motive that I just find profoundly unconvincing.

It actually doesn't, the point of it is to escape uniformity of motive. If galactic colonization is not merely inconvenient, but has intractable problems of some sort which throttle it, societal motivations don't matter - it's just not going to happen much, or maybe ever depending on the nature of the problems and how parallel universal sapient development is. One possible solution is that building something in your own star system is just so superior to colonizing the galaxy that nobody ever really gets too far from their home systems before just doing that instead.

The bottom line is that if that actually is an alien civilization building a megastructure, their existence implies that it is very unlikely that interstellar colonization is something we'll ever actually do, even if we don't understand the reasons yet. If we look closer and find out that they are colonizing systems even while building this thing, that they're expanding outwards in a manner consistent with eventual galactic colonization within the next hundred million years or so, then we'd better hope that galactic colonization actually is a terrible idea and we just managed to spot them before they figured it out themselves and stopped completely. Otherwise that implies that there's a very high probability that oh shit oh shit oh shit fuck fuck fuck fuck fuck.

The other implication if that were an actual alien race would be that it'd suggest the Great Filter is still ahead of us.

I find the assumptions behind the theory of a Great Filter deeply flawed. There is an assumption that life would both be able to spread through the universe and would want to.

While self-replicating machines etc could be created, what would be its purpose? Life spread across Earth because it was to the advantage of those alive then, what immediate purpose does it serve to send out self-replicating machines that would never return home?

As I said, the very notion of universal colonisation could be false. If FTL travel is impossible then colonisation may be implausible. In which case there may not be a Great Filter as sentient life could be abundant throughout the universe but undetectable to us.

Originally Posted by Ominous Gamer

Being upset is understandable, but be upset at yourself for poor planning, not at the world by acting like a spoiled bitch during an interview.

In other words, they are superior in some way. It's easier than trying to maintain an army of swordsmen large enough to guarantee annihilation of our enemies within quick striking distance of them. You don't need to understand why they're superior to understand that they are.

So, if they're so superior why don't they get used in any conflicts? In fact, they must be inferior to our conventional weapons because we never use them. Right?

It's unlikely that they're the first. If there are two sapient races, then there are almost certainly many. If the reasons are political or cultural, then you need to assume that all races have political or cultural reasons not to do it. I consider this unlikely, but if it were true there's no reason to assume we'll be any different at that stage. The difference between this and assuming that there is some logistical reason not to do it is negligible right now.

I think the assumption here that I have an issue with is that the cost-benefit analysis of total colonisation vs limited colonisation vs megastructure buidling is uniform across all of time and space. Just because it makes no sense for them to do it now, in this part of the universe doesn't mean it won't make sense for them, us, or someone else, to do it at some other point in time or some other part of the universe.

The assumption is also that regions of space, once colonised will stay colonised more or less indefinately.

This is that massive coincidence again, though. On further reflection of the likelihood of this, I can only pray that this isn't the case. For colonization to be worth doing, and for it to not have happened until now, and for sapient life to be so common that two races could coexist so close in time and space, it won't matter how far off their expansion horizon is from us - we are almost certainly thoroughly fucked. The Great Filter will be ahead of us, and it is going to be angry.

The Great Filter will learn to *fear* us.

This is solved by a version of the anthropic principle. Our conversation here is nothing special. I could be having a similar conversation on some other forum, or with someone else. If you weren't here, I'd probably be doing something equivalent with EyeKhan. Right now, other people besides the two of us are probably having similar conversations. Nothing is special about what we're doing right now, so it's a believable outcome.

I am trying not to be offended here.

The same cannot be said about the idea that they exist, are colonizing the galaxy, but haven't gotten to us yet. That would place both us and them in a privileged position in the history of the galaxy. It's not impossible, but it's extremely unlikely, only more so because the galaxy has been capable of supporting life such as our for billions of years before now.

The situation can only be resolved by assuming there's nothing special about our situation. We aren't privileged. If we had existed at some other time in the the past or next billion years instead, or in some other galaxy, we would still be able to look out and see most stars empty, with a scant handful stars having megastructures built around them. The only way this can be true (if that is a megastructure we're seeing), the only way to maintain our unprivileged status, is if interstellar colonization just isn't a route civilizations go down, for whatever reason. Otherwise, the universe doesn't meet what we should expect as unprivileged observers.

Alternative theories:

* if life on Earth began elsewhere that would potentually add billions more years to the timescale of the evolution of life meaning that it is only around now that intelligent life begins to develop
* Once intelligent life is advanced enough, it stops expressing itself in ways which are detectable to us

It actually doesn't, the point of it is to escape uniformity of motive. If galactic colonization is not merely inconvenient, but has intractable problems of some sort which throttle it, societal motivations don't matter - it's just not going to happen much, or maybe ever depending on the nature of the problems and how parallel universal sapient development is. One possible solution is that building something in your own star system is just so superior to colonizing the galaxy that nobody ever really gets too far from their home systems before just doing that instead.

The problem I have with this is that intersteller colonisation is plausible even with current or near future technologies (although not easy); certainly more plausible than megascale engineering, so it's hard to imagine what would keep civilisations from doing it *across the board*; especially when some races may find it a lot easier than we do - if they're on a world with lower gravity, getting into orbit isn't such a pain in the ass, races longer lived or less suseptable to radiation damage would find space travel a lot easier etc. I mean, space travel is hard but not that hard.

The bottom line is that if that actually is an alien civilization building a megastructure, their existence implies that it is very unlikely that interstellar colonization is something we'll ever actually do, even if we don't understand the reasons yet. If we look closer and find out that they are colonizing systems even while building this thing, that they're expanding outwards in a manner consistent with eventual galactic colonization within the next hundred million years or so, then we'd better hope that galactic colonization actually is a terrible idea and we just managed to spot them before they figured it out themselves and stopped completely. Otherwise that implies that there's a very high probability that oh shit oh shit oh shit fuck fuck fuck fuck fuck.

Alternatively, a species rate of technological progress is no constant; after a certain point you reach more of a plateau and we'll catch them up before they get near us.

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

So, if they're so superior why don't they get used in any conflicts? In fact, they must be inferior to our conventional weapons because we never use them. Right?

They are being used, they're just not being detonated. They cannot possibly be replaced by swords, no matter how big - swords just can't hope to accomplish the same things.

Also, I was trying to steer it towards "bombs" and not just nukes because you really need to see the full suite of what were doing instead of medieval weapons for the comparison. But we're already pretty far off track here now.

I think the assumption here that I have an issue with is that the cost-benefit analysis of total colonisation vs limited colonisation vs megastructure buidling is uniform across all of time and space. Just because it makes no sense for them to do it now, in this part of the universe doesn't mean it won't make sense for them, us, or someone else, to do it at some other point in time or some other part of the universe.

The assumption is also that regions of space, once colonised will stay colonised more or less indefinately.

If it's ever a good idea, then in a high sapient population universe (which there mere existence would imply - one species might be an anomaly, but two so close implies many about), then colonization should have already been done to death. We're also at least 4 billion and probably closer to 8 billion years late to the party - the universe should be packed if colonization were the way to go for anyone at any time. Once colonization starts, it should be virtually unstoppable, because once one system successfully sends out colony ships, now you have many systems with the tech to colonize the stars and they all have proof that it's a good idea.

Maybe some disasters will locally wipe out some populations, but on a cosmological scale then yes, once a region becomes colonized it should stay colonized until that becomes impossible (probably the degenerate era). Otherwise, this implies that races never get more than one or two steps outside of their star before somehow dying out totally, leaving nobody to recolonize. That isn't substantially different from no colonization at all.

Alternative theories:

* if life on Earth began elsewhere that would potentually add billions more years to the timescale of the evolution of life meaning that it is only around now that intelligent life begins to develop
* Once intelligent life is advanced enough, it stops expressing itself in ways which are detectable to us

The first one seems pretty unlikely, as if intelligent life were only now emerging into the universe but was doing so in large numbers it would mean we're one of the first races out of the gate. It would mean there's nothing special about our evolutionary history, except that we were faster at it than most. I guess maybe it's true, but damn that'd make us incredibly lucky. This also seems to go against what I know of evolutionary history - there were a couple big leaps that had to get made, and it should have been just chance that made them take as long as they did. There should be races far luckier than ours even if all/most life comes from panspermia.

I can't come up with any strong objections to the second at the moment, as it's stated.

The problem I have with this is that intersteller colonisation is plausible even with current or near future technologies (although not easy); certainly more plausible than megascale engineering, so it's hard to imagine what would keep civilisations from doing it *across the board*; especially when some races may find it a lot easier than we do - if they're on a world with lower gravity, getting into orbit isn't such a pain in the ass, races longer lived or less suseptable to radiation damage would find space travel a lot easier etc. I mean, space travel is hard but not that hard.

Some could leak out of their systems, as long as they figure out that it's a mistake before they get too many generations into it. If it stays a good idea in the long term for even one civilization, we get back to the problem of how the galaxy should be filled, but if colonization is anomalous whenever it happens, a mistake that gets fixed or contained, then we can have a populated galaxy with our system still being uncolonized.

Alternatively, a species rate of technological progress is no constant; after a certain point you reach more of a plateau and we'll catch them up before they get near us.

It's not them I'd be afraid of. It's whatever the thing is that keeps killing off other technological species before they can catch up to where those guys are right now. If they are anomalous, we can't count on being as lucky as them.

I find the assumptions behind the theory of a Great Filter deeply flawed. There is an assumption that life would both be able to spread through the universe and would want to.

While self-replicating machines etc could be created, what would be its purpose? Life spread across Earth because it was to the advantage of those alive then, what immediate purpose does it serve to send out self-replicating machines that would never return home?

As I said, the very notion of universal colonisation could be false. If FTL travel is impossible then colonisation may be implausible. In which case there may not be a Great Filter as sentient life could be abundant throughout the universe but undetectable to us.

The Great Filter is just the the main thing that stops dead matter from giving rise to life that expands throughout the unverse and persists forever. It could be anything (almost, we've ruled out a couple things), and we may or may not be past it already.

They are being used, they're just not being detonated. They cannot possibly be replaced by swords, no matter how big - swords just can't hope to accomplish the same things.

Also, I was trying to steer it towards "bombs" and not just nukes because you really need to see the full suite of what were doing instead of medieval weapons for the comparison. But we're already pretty far off track here now.

Distant observers (in space or time) would not have access to the full suite of what we are doing, just like we don't have access to the full suite of what the KIC guys are up to.

The first one seems pretty unlikely, as if intelligent life were only now emerging into the universe but was doing so in large numbers it would mean we're one of the first races out of the gate.

We *are* one of the first races out of the gate; the universe is only 14 billion years old and most models of the ultimate fate of the universe have it remaining this way for at least tens of billions and possibly trillions more. Assuming those models are correct, we're in a very young universe.

It would mean there's nothing special about our evolutionary history, except that we were faster at it than most. I guess maybe it's true, but damn that'd make us incredibly lucky.

It doesn't necessarily make us the first or even close to the first, it just lowers the amount of time in which other intelligent races can potentially have been kicking around out there quit drastically (from billions down to millions); therefore potentially explaining the lack of evidence we see for them.

I can't come up with any strong objections to the second at the moment, as it's stated.

The more I think about it the more sense it makes, our science has already begun shown us that the reality we perceive in our day to day lives and the reality as it actually exists are not the same thing, and questions such as why the universe exists and is the way it is are currently completely beyond us; it makes sense that as a civilisation advances in knowledge over a period of millions of years they will come to understand our reality in ways we cannot even comprehend and will, presumably, also develop technology anchored in that understanding.

Some could leak out of their systems, as long as they figure out that it's a mistake before they get too many generations into it. If it stays a good idea in the long term for even one civilization, we get back to the problem of how the galaxy should be filled, but if colonization is anomalous whenever it happens, a mistake that gets fixed or contained, then we can have a populated galaxy with our system still being uncolonized.

An related idea is that intersteller colonisation *is* a good idea until you reach a certain point of development at which point it stops becoming a worthwhile endeavour. This may happen in fits and starts. For example:

* Interseller colonisation is current theoretically possible but very expensive so not worthwhile
* Technology develops; now it's worthwhile because it's cheaper and we're running out of living space
* A few hundred years later and now technology has developed to the point where we can build things like Halos/Culture orbitals and other elaborate megastructures to live on, so we don't need to expand into other stellar systems for more living space; we still do it sometimes just for the hell of it but there's no massive push to expand as there was in previous eras and expansion slows to a crawl
* Thousands of years later our society is so fantastically advanced we now need dyson spheres to meet our energy needs so we have to start expanding other stars again to meet our resource needs.
* Perhaps a million years on we're now so advanced we can now manipulate reality itself and everyone just moves into the giant Tardis we made

Truth serves them
Embrace and defend her case
Part flattery, part threats
"For those who cling to this domination will partake in its fall"

The Great Filter is just the the main thing that stops dead matter from giving rise to life that expands throughout the unverse and persists forever. It could be anything (almost, we've ruled out a couple things), and we may or may not be past it already.

I think the idea we're past the filter to be quite hubristic.

Originally Posted by Ominous Gamer

Being upset is understandable, but be upset at yourself for poor planning, not at the world by acting like a spoiled bitch during an interview.

I don't have an answer for the Fermi Paradox, but I think many of you are vastly overestimating the ease with which we could establish an interstellar colony. Current propulsion technologies just aren't really good enough to move anything of substantial mass such a long distance - especially since we'd need to slow down at the end. There are fundamental limits based on the energy density of our currently available fuels. Sending enough technology to establish a self-sustaining habitat in an unknown and likely hostile environment isn't just expensive - it's damn near impossible with our current level of technology. There's a tradeoff here - you either need vast resources to keep a generation ship alive, which dramatically increases the weight of your payload, or you need very high speeds, which isn't practical for anything but the smallest of payloads.

That's ignoring the fundamental issues with technology mooted by Vinge and others - to set up a high-technology society at interstellar distances you need a surprising amount of stuff and population. This isn't Mars, where we could imagine robotic ships providing a regular supply of high technology goods to keep things going. This is at distances so far that everything needs to be self-sustaining - from materials sourcing to purification to manufacturing to repairs. It requires a lot of people and a lot of equipment. Some people have tried to estimate just how much population would be required to support our current level of technology on Earth, and the numbers are often in the tens of millions. Even if you ruthlessly cut this number down by eliminating positions of marginal importance, you still need an enormous critical mass, especially given the challenges posed by the (likely) hostile colonial environment (which eliminates the possibility of establishing a low tech colony). One could imagine technological breakthroughs in robotics, AI, and nanotechnology that might address this issue, but for now those technologies are science fiction. Self-perpetuating technology simply doesn't exist.

If propulsion gets dramatically better, it will at least be feasible, even if ruinously expensive, to set up a colony. But absent a lot of other fundamental shifts in technology, there's no way it's going to appear to be worth it.

"When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first." - Werner Heisenberg (maybe)